98 k2500 jerking on deceleration
 

Hi everyone just purchased a 98 k2500 6.5 with a manual trans 230,000 miles truck seems to pull pretty decent with no problems 3rd its a bit of a dog had someone drive it and said it was way under power so far i have replaced the pmd and relocated it changed all 8 glow plugs along with the fuel filter the lift pump when I go to downshift with the rpms past 1500 it jerks really bad like im tapping the throttle really fast goes away when i push the clutch in when I had a mechanic check it out it jerked so bad that it almost died and went into a limp mode anytime you tried to give it throttle the rpms would go to 1500 and drop again and again shut the key off started it back up it was fine the truck pulled 2 codes one was a slow injection timing the other was a bad thermostat any help would be appreciated since I have called many diesel mechanics and no one knows what it is

Post the actual code #'s,most code readers give the wrong deffinition for the code shown-these seem to have an orphan code description vs a gasser.

The codes that I pulled were a p0126 and a p1216 I have found out that if I let it jerk long enough on compression that the engine shuts down and if im sitting there in neutral and rev the engine really quick that the rpms stay up and jumps around between 1800-2500 before dropping to an idle i could post a video if that would help

P0126 Insufficient ECT for Stable Operation
P1216 Fuel Solenoid Response Time Short

Coolant sensor/thermostat problem and PMD/IP related issue?